1. Field of the Invention
The present invention generally relates to methods of reproducing visual images, and more particularly, to those methods for reproducing visual images in three-dimensional form.
2. General Background
A number of methods for producing three-dimensional images from two-dimensional means have existed. These fall into two groups: the "stereoscope method" group and the "Pepper's Ghost" method group. One of the first methods of producing a three-dimensional effect employed a device called a stereoscope. This device employed a method whereby two photographs of the same scene were taken at slightly different angles and were viewed through two eye pieces. The apparatus and methods for producing three-dimensional effects progressed through a phase whereby the two images were projected side by side onto a screen. Members of the audience held stereoscope type viewers in their hands and aimed at the screen, aligning them as best they could so that the right image came only to their eye while the image came only to their left eye.
A significant improvement was made with the "colored filter/glasses" method (a variation of the stereoscope method group) in which two black and white photographs of the same scene were taken at slightly different angles. Two projectors were used, one projecting the right image and the other projecting the left image. The two projectors were aligned with respect to the screen so that their images were superimposed over each other on the screen.
Over the lenses of the projectors were placed an unmatched set of colored filters, each filter passing a narrow range of wavelengths of light while blocking other wavelengths. The set of filters were "unmatched" in that each passed a range of wavelengths exclusive of the range passed by the other.
An identical set of unmatched colored filters were given to the audience for use as glasses, each filter passing a narrow range of wavelengths of light, each exclusive of the other. The filter over the audience's right eye matched the filter on the right projector. The filter over the audience's left eye matched the filter over the left projector.
Thus, on leaving the right projector, the right image was "colored" to a narrow range of wavelengths of light which would, after bouncing off the screen, pass through the filter on the right eye of the audience's glasses and enter the right eye and thus be seen by the right eye but not enter the filter over the left eye and therefore not be seen by the left eye. Conversely, on leaving the projector the left image was "colored" to a narrow range of wavelengths of light which would, after bouncing off the screen, pass through the filter on the left eye of the audience's glasses and enter the left eye and therefore be seen by the left eye but not enter the filter on the right eye of the audience's glasses and therefore not be seen by the right eye.
Thus, through the use of these colored projector filters and colored glasses, each eye would see a separate image, producing a stereoscopic effect.
With the development of polarizing materials, a significant advance was made in the ability to project three-dimensional images in color. Two separate images were photographed in color, from slightly different angles, one for the viewer to see through his right eye, one image to be seen through the left. The separate images were projected through respective lenses on to a screen where they were superimposed, one upon the other. Polarizing filters were placed over the film projector lenses and adjusted so that the polarizing axis of one polarizing filter was displaced by 90 of arc from the polarizing axis of the other. The viewer uses specially prepared polarized glasses with each of the lenses being polarized to match the process initiated at the projector. For example, the right lens of the audience's glasses was polarized vertically so as to receive only the vertically polarized light from the right projector; the left lens of the audience's glasses was polarized horizontally so as to receive only the light waves from the projector which were oriented horizontally. Thus, through the use of polarizing lenses, each eye would see a separate image producing a stereoscopic effect. It is important to note that all of the prior art methods above (the stereographic method group) have the advantages of being able to use still pictures, motion pictures or video pictures as their images sources but all of the prior art methods above have the distinct disadvantage of requiring the audience to view the image through glasses or stereoscopes or some other device kept close to the face. This is inconvenient and uncomfortable for the audience. The glasses or other devices are expensive and their re-use by other audiences causes a potential health hazard.
Theatrical illusions have been created which give the viewer the effect of a three-dimensional scene. These are typically known as "Pepper's Ghost" or "Cabaret du Neant." The illusion is based on elementary optical effects. A viewer is place in a specific area and typically views fixed, three-dimensional theatrical sets, e.g., tables, chairs, through a reflective transplant medium such as glass. The reflective transparent medium through which the viewer sees the props is placed at an angle to the viewer to produce a reflecting surface. A lighted object which is to appear to be in the theatrical scene is placed out of sight of the viewer but is accurately placed such that the viewer sees the reflection of the lighted object via the reflecting medium. Since the reflection of the lighted object is from the reflection of the light from the surface of the transparent medium, the viewer will see a "virtual image" of the lighted object in juxtaposition with the theatrical props. The three-dimensional images created through the use of this illusion technique have inherent limitations. If the virtual image is to be three-dimensional, then the lighted object must be a solid three-dimensional object rather than a two-dimensional film or video image. This limitation substantially reduces the flexibility of the system since three-dimensional objects are more difficult and expensive to manipulate than are two-dimensional film or video images.
Some of these devices have used single projectors however, only a single image has been generated. When one image is seen directly and one seen by reflection, unevenness in illumination may result. Absorption filters have been used to prevent light contamination of the images, resulting from image generation along different axes. If multiple projectors, were used to create a multiple image synchronization would be required.
Devices have been suggested for three-dimensional television projection systems designed apparently for home viewing. Multiple television projection screens were used. They have required a positive lens to reposition the composite picture formed forward to a viewing audience. It does not appear that these are suitable for theatrical use before a significant live audience.
The present invention method substantially resolves the problems which are inherent in those methods disclosed in the prior art. No stereoscopic device or glasses are required yet three-dimensional images are created irom two-dimensional images without the need for solid three-dimensional objects. Only a single projection source is required, limiting capital expenditures and eliminating the need for projection synchronization. Yet the invention is suitable for theatrical viewing before a stage audience. Moreover, the three dimensional image generated from the single two dimensional source may be integrated with three-dimensional images irom a live stage which may use props or actors.